A theoretical model describing photophysics of pi-conjugated aggregates, such as molecular crystals and polymer thin films, is developed. A Holstein-like Hamiltonian expressed with a multi-particle basis set is used to evaluate absorption and photoluminescence (PL) spectra of neutral excitons as well as charge modulation spectra (CMS) and transient absorption spectra (TAS) of positively charges hole-type polarons. The results are used to develop a better theoretical understanding of the organic electronics being studied and their photophysics, and also to probe the morphology of poly(3-hexylthiophene) (P3HT) thin films, which are used in photovoltaic devices. |